Too low res so that HD version will be a must. It also made me feel sick as a pig but other than that I was very impressed.

HL2 is hard on your vr legs and was the only game that gave me bad motion sickness. But once i had the right config(using Teamfortress 2 setup) and plugged it into half life and stood up while playing and used a controller it is much, much better.
I think the movement is too quick in HL2 especially from standing still and using a controller helps this a lot.
Check out Titans of Space , that is a very good demo and will not give you motion sickness.